Transcriptomic analysis and novel insights into lens fibre cell differentiation regulated by Gata3

Gata3 is a DNA-binding transcription factor involved in cellular differentiation in a variety of tissues including inner ear, hair follicle, kidney, mammary gland and T-cells. In a previous study in 2009, Maeda et al . ( Dev. Dyn. 238 , 2280–2291; doi:10.1002/dvdy.22035 ) found that Gata3 mutants could be rescued from midgestational lethality by the expression of a Gata3 transgene in sympathoadrenal neuroendocrine cells. The rescued embryos clearly showed multiple defects in lens fibre cell differentiation. To determine whether these defects were truly due to the loss of Gata3 expression in the lens, we generated a lens-specific Gata3 loss-of-function model. Analogous to the previous findings, our Gata3 null embryos showed abnormal regulation of cell cycle exit during lens fibre cell differentiation, marked by reduction in the expression of the cyclin-dependent kinase inhibitors Cdkn1b/p27 and Cdkn1c/p57, and the retention of nuclei accompanied by downregulation of Dnase IIβ. Comparisons of transcriptomes between control and mutated lenses by RNA-Seq revealed dysregulation of lens-specific crystallin genes and intermediate filament protein Bfsp2. Both Cdkn1b/p27 and Cdkn1c/p57 loci are occupied in vivo by Gata3, as well as Prox1 and c-Jun, in lens chromatin. Collectively, our studies suggest that Gata3 regulates lens differentiation through the direct regulation of the Cdkn1b/p27and Cdkn1c/p57 expression, and the direct/or indirect transcriptional control of Bfsp2 and Dnase IIβ.

Mapping thermal conductivity across bamboo cell walls with scanning thermal microscopy

Scanning thermal microscopy is a powerful tool for investigating biological materials and structures like bamboo and its cell walls. Alongside nanoscale topographical information, the technique reveals local variations in thermal conductivity of this elegant natural material. We observe that at the tissue scale, fibre cells in the scattered vascular tissue would offer preferential pathways for heat transport due to their higher conductivities in both anatomical directions, in comparison to parenchymatic cells in ground tissue. In addition, the transverse orientation offers more resistance to heat flow. Furthermore, we observe each fibre cell to compose of up to ten layers, with alternating thick and thin lamellae in the secondary wall. Notably, we find the thin lamellae to have relatively lower conductivity than the thick lamellae in the fibre direction. This is due to the distinct orientation of cellulose microfibrils within the cell wall layers, and that cellulose microfibrils are highly anisotropic and have higher conductivity along their lengths. Microfibrils in the thick lamellae are oriented almost parallel to the fibre cell axis, while microfibrils in the thin lamellae are oriented almost perpendicular to the cell axis. Bamboo grasses have evolved to rapidly deposit this combination of thick and thin layers, like a polymer composite laminate or cross-laminated timber, for combination of axial and transverse stiffness and strength. However, this architecture is found to have interesting implications on thermal transport in bamboo, which is relevant for the application of engineered bamboo in buildings. We further conclude that scanning thermal microscopy may be a useful technique in plant science research, including for phenotyping studies.

Combined elevated temperature and soil waterlogging stresses limit fibre biomass accumulation and fibre quality formation by disrupting protein activity during cotton fibre development

Soil waterlogging and high temperature conditions generally occur together, especially in the Yangtze River Valley, China, negatively affecting cotton (Gossypium hirsutum L.) fibre development. Therefore, combined elevated temperature (34.1/29.0°C) and soil waterlogging (6 days) were imposed to study their combined effects on fibre biomass and fibre qualities (length, strength and micronaire). The results showed that in the boll cohort exposed to waterlogging and/or elevated air temperature, combined elevated temperature and soil waterlogging decreased final fibre length (by 8.9–11.3%) and fibre biomass (by 25.8–33.9%) more than either stress individually. A total of 113, 263 and 290 differential abundance proteins were identified related to elevated temperature, waterlogging and the two treatments combined, respectively, in fibres at 15 days after anthesis via the isobaric tags for relative and absolute quantitation technique, which were classified as: carbohydrate and energy metabolism (21.7%), protein metabolism (16.6%), amino acid metabolism (12.8%), intracellular structural components (6.6%), transport (7.9%), oxidation–reduction process (7.9%), signal transduction (5.2%), lipid metabolism (5.2%), stress response (5.2%), nucleic acid metabolism (4.5%), organic acid metabolism (3.4%) and others (2.1%). Both vacuolar ATPase (V-ATPase) and plasma membrane H+-ATPase (PMH+-ATPase) were responsible for fibre length formation, although V-ATPase expression may play a major role in determining fibre cell elongation rather than PM H+-ATPase expression. It was concluded that fibre cell elongation and secondary wall thickening were inhibited mainly by reduced accumulation of osmolytes, blocked synthesis and transport of secondary wall components, and disruption of the cytoskeleton system under combined elevated temperature and soil waterlogging.

Resistance of the S1 layer in kempas heartwood fibers to soft rot decay

Naturally durable heartwoods, where available, continue to be used as support structures in environments considered hazardous, particularly in ground contact. However, durability of heartwoods against wood decay microorganisms varies. Therefore, it is important to evaluate heartwood products for their in-service performance in order to maximise benefits derived from this valuable natural resource of limited supply. In the work presented, wood pieces from a kempas (Koompassia malaccensis) utility pole that had been placed in service in an acidic soil in Malaysia, and in time had softened at the ground-line position, were examined by light and transmission electron microscopy to evaluate the cause of deterioration.Light microscopy (LM) provided evidence of extensive attack on fibre cell walls by cavity-producing soft rot fungi. Transmission electron microscopy (TEM) revealed in greater detail the distribution and micromorphologies of cavities as well as their relationships to the fine structure of fibre cell walls, which consisted of a highly electron dense middle lamella, a moderately dense S1 layer and a multilamellar S2 layer with variable densities, reflecting differences in lignin concentration. The resistance of the moderately dense S1 layer to soft rot was a feature of particular interest and is the main focus of the work presented. The resistance appeared to be correlated with high lignification of the outermost region of the S2 wall, interfacing with the S1 layer, an unusual cell wall feature not previously described for normal wood.